Hello,
My Manager and I were sat at work watching a small rescue / ambulance helicopter hover over a large road this morning.
The follow conversation followed:
Me - "I wonder how much fuel they use per hour?"
Him - "It must use more fuel hovering than it does flying forward"
Me - "Surely not, it's not as effected by air friction"
Him - "I bet you lunch that you're wrong"
Me - "Deal"
Can you help solve this argument / win me lunch?
I appreciate there are a ton of variants and the question makes no mention of specifics, but can you help?
Thank you in advance!

alright. here's how you win. yes it takes more power(fuel) to hover than to sustain forward flight, BUT because it is EMS they will most likely pull max torque to achieve the highest airspeed possible, burning more fuel/hour.
send me a gift card, i want lunch too!

To be sure, you're saying that it uses more fuel to hover than it does to fly forward? Surely while flying forward the helicopter is having to counter gravity, wind and air friction; whereas while hovering the helicopter is only countering gravity and wind? Therefore more fuel is used while flying forwards than when hovering.

Posted By Tribes on 01/17/2012 7:04 AMHello,
My Manager and I were sat at work watching a small rescue / ambulance helicopter hover over a large road this morning.
The follow conversation followed:
Me - "I wonder how much fuel they use per hour?"
Him - "It must use more fuel hovering than it does flying forward"
Me - "Surely not, it's not as effected by air friction"
Him - "I bet you lunch that you're wrong"
Me - "Deal"
Can you help solve this argument / win me lunch?
I appreciate there are a ton of variants and the question makes no mention of specifics, but can you help?
Thank you in advance!

With other variables held constant, the rate of fuel
consumption is directly proportional to power being developed which is normally
equal to the “Power Required”. There’s a power required, airspeed, fuel flow
relationship. You can see that relationship from the figure below.
Parasite drag accounts for the "air friction"
he's talking about, but don’t forget about induced drag.

While hovering induced drag is high, power required is high,
and fuel flow is high. As the helicopter moves into forward flight and airspeed
increases, the rotor system starts to work on larger volumes of air per-second
and the induced drag, power required, and fuel flow decrease.

iMac,
Thanks for your concise reply.
From what you've said can I put it in a way that my tiny little mind can understand?:
Hovering = High fuel consumption
Low speed forward flight = Low fuel consumption
High speed forward flight = High fuel consumption
There is a sweet spot at which low speed flight uses less fuel than hovering.
Much appreciated.

Posted By Tribes on 01/17/2012 3:21 PMiMac,
Thanks for your concise reply.
From what you've said can I put it in a way that my tiny little mind can understand?:
Hovering = High fuel consumption
Low speed forward flight = Low fuel consumption
High speed forward flight = High fuel consumption
There is a sweet spot at which low speed flight uses less fuel than hovering.
Much appreciated.

This might also help. In our Robinson R22's the most fuel efficient cruise speed is 83 knots. The speed at which we stay airborne the longest is 53 knots. So, if you go out to an oil rig and it blows up you want to try to return at 83 knots to someplace or hover around at 53 knots waiting for the rig to burn out. Our solo topspeed is 102 knots and that would be a fast cruise. You might use more power at hover than you would at any of these speeds. Medivac would by fast cruise to get the patient to the hospital. In our photo flights the helicopter is usually heavy with two guys onboard but our manuevers are near the 53 knot average. If you are going faster or slower than 53 knots optimal fuel sipping speed you burn more fuel. Perhaps a hovercraft is the only other "vehicle" the uses more fuel to go slower.